1. Field of the Invention
The present invention relates to a color-television receiver with at least one digital integrated circuit for processing the composite color signal.
2. Description of the Prior Art
A color-television receiver is described in Offenlegungsschrift DE No. 28 54 236 Al, in which the composite color signal is processed there by all-digital circuitry. To accomplish this, the color-television receiver contains a squarewave clock generator for generating at least three clock signals which serves as a chrominance-subcarrier oscillator. The first clock signal is at four times the chrominance-subcarrier frequency, while the two other clock signals are at the chrominance-subcarrier frequency, with the first and the second clock signal having a 1:1 mark/space ratio. The prior art color-television receiver further includes an analog-to-digital converter which is clocked by the first clock signal and whose analog input is presented with the composite color signal. At the instants the respective amplitudes of the undemodulated chrominance signal are equal to the amplitudes of the respective color-difference signal, the analog-to-digital converter forms a parallel binary word from the amplitude of the composite color signal, and a subcircuit is provided which generates the digital Red-minus-Luminance difference signal and the digital Blue-minus-Luminance difference signal, i.e., the R-Y color-difference signal and the B-Y color-difference signal.
In circuits of color-television receivers using analog signal processing, the chrominance-subcarrier oscillator is commonly locked in frequency and phase to the received chrominance subcarrier, which is transmitted in the form of so-called color bursts. The burst is first separated from the composite color signal by means of a suitably conditioned keying signal and then used for synchronizing purposes; cf. the book by O. Limann entitled "Fernsehtechnik ohne Ballast", 12th Edition, Munich, 1978, pages 209 to 217.